(1) Field of the Invention
This invention relates to an apparatus having a charge coupled device, and more particularly to an apparatus having a charge coupled device which is so constructed that a part of charge which is discharged from electrodes of the charge coupled device is reused to charge other electrodes, thereby reducing power consumption, and heat dissipation losses and enabling the miniaturization of the apparatus.
(2) Description of the Prior Art
The charge coupled device (CCD) has originally been developed as a shift register or a delay line, which at present is developed to be applied widely to an image pickup apparatus by the use of its photoelectric conversion function.
FIG. 1 is a sectional view exemplary of the conventional CCD of the two-phase type, in which reference numeral 1 designates a semiconductor substrate of silicon, and numeral 2 designates an insulating layer of silicon dioxide over the substrate 1, and numerals 31, 31', 32 and 32' designate electrode groups disposed on the insulating layer 2, which comprise a large number of first electrode pairs 310 of upper and lower electrodes 31 and 31' connected to each other and of second electrode pairs 320 of adjacent upper and lower electrodes 32 and 32' connected to each other, the electrode pairs 310 and 320 being disposed alternately.
The conventional apparatus using the CCD constructed as the above, as shown in FIG. 2, applies a drive pulse .phi. from a first drive circuit 51 to a capacitor C.sub.1 representing the gross capacity of a large number of first electrode pairs 310 of CCD 4, and simultaneously drive pulse .phi. from a second drive circuit 52 to a capacitor C.sub.2 representing the gross capacity of a large number of second electrode pairs 320 of CCD4, so that a potential well V formed at the semiconductor substrate 1 moves as shown by the broken line in FIG. 1 whereby the charges, for example, electrons, which are trapped by the potential well V, are transferred.
The first and second drive circuits 51 and 52 amplify clock pulses CLK and CLK from clock oscillators to the predetermined voltage values respectively. Concretely, a drive circuit 5, as shown in FIG. 3, is used, in which between the constant voltage source E and ground, a series circuit is connected which consists of a resistance R.sub.1, a transistor T.sub.1 whose base is supplied with clock pulse CLK, and a resistance R.sub.2 ; a series circuit consists of a resistance R.sub.3, a transistor T.sub.2 whose base is connected to the collector of transistor T.sub.1, a diode D and a transistor T.sub.3 whose base is connected to the emitter of transistor T.sub.1, are connected in parallel to the first series circuit, and the transistor T.sub.3 collector is connected to a capacitor C formed between the electrodes 31, 31 . . . , 31', 31'. . . and 32, 32 . . . , 32', 32'. . . and the substrate 1. In other words, when the clock pulse CLK changes from a "H" (high) level to a "L" (low) level, the transistor T.sub.1 is off, T.sub.2 is on, and T.sub.3 is off, so that a charging current from the constant voltage source E flows into the capacitor C of the CCD 4 through the resistance R.sub.3, transistor T.sub.2 and diode D. Conversely, when the clock pulse CLK changes from "L" level to "H" level, the transistor T.sub.1 is on, T.sub.2 is off, and T.sub.3 is on, so that a discharge current ib flows to ground through the transistor T.sub.3.
FIG. 4 is a structural view exemplary of the conventional solid image pickup apparatus applying the aforesaid apparatus having a charge coupled device.
In the same figure, reference numeral 40 designates an image pickup device comprising the CCD shown in FIG. 1. The image pickup device 40 comprises an image pickup unit 4P receiving optical images and photoelectrically converting them to obtain charge images, a storage unit 4A into which the charge images from the image pickup unit 4P are transferred and received therein and then temporarily stored, and a horizontal transfer unit 4H which transfers and outputs the charge images of storage unit 4A each scanning line. Reference numerals 51P, 52P, 51A, 52A, 51H and 52H designate drive circuits as shown in FIG. 3 respectively, which supply drive pulses .phi.P, .phi.P, .phi.A, .phi.A, .phi.H and .phi.H to the image pickup unit 4P, storage unit 4A and horizontal transfer unit 4H at the image pickup element 40 on the basis of clock pulses CLK-P, CLK-P, CLK-A, CLK-A, CLK-H and CLK-H.
In such conventional image pickup apparatus, the first and second electrode pairs 310 and 320 which are supplied with drive pulses .phi. and .phi. are provided as shown in FIG. 1 throughout the overall surfaces of image pickup unit 4P, storage unit 4A and horizontal transfer unit 4H at the image pickup element 40, resulting in a capacitor of large capacity being formed between the electrode pairs 310 and 320 and the grounded semiconductor substrate 1, the capacity being in the range of between several hundreds of PF through several thousands of PF.
Hence, the charging and discharge currents from the drive circuits 51P, 52P, 51A, 52A . . . to the image pickup element 40 become larger, whereby the consumption current becomes larger and the heat dissipation losses increase, thus requiring a fairly large radiator for heat radiation. Hence, in a case where such a charge coupling apparatus is used in, for example, an image pickup apparatus, a problem occurs in that the image pickup apparatus is difficult to miniaturize.